Don't run 'pub list-package-dirs' if there is no pubpsec.lock file.

pkg/analyzer/lib/source/pub_package_map_provider.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library source.pub_package_map_provider;
 
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:core' hide Resource;
 import 'dart:io' as io;
@@ skipping 41 matching lines @@
    * A [RunPubList] implementation may be injected for testing
    */
   PubPackageMapProvider(this.resourceProvider, this.sdk, [this._runPubList]) {
     if (_runPubList == null) {
       _runPubList = _runPubListDefault;
     }
   }
 
   @override
   PackageMapInfo computePackageMap(Folder folder) {
+    // If the pubspec.lock file does not exist, no need to run anything.
+    {
+      String lockPath = getPubspecLockPath(folder);
+      if (!resourceProvider.getFile(lockPath).exists) {
+        return computePackageMapError(folder);
+      }
+    }
     // TODO(paulberry) make this asynchronous so that we can (a) do other
     // analysis while it's in progress, and (b) time out if it takes too long
     // to respond.
     io.ProcessResult result;
     try {
       result = _runPubList(folder);
     } on io.ProcessException catch (exception, stackTrace) {
       AnalysisEngine.instance.logger.logInformation(
           "Error running pub $PUB_LIST_COMMAND\n$exception\n$stackTrace");
     }
@@ skipping 17 matching lines @@
   }
 
   /**
    * Create a PackageMapInfo object representing an error condition.
    */
   PackageMapInfo computePackageMapError(Folder folder) {
     // Even if an error occurs, we still need to know the dependencies, so that
     // we'll know when to try running "pub list-package-dirs" again.
     // Unfortunately, "pub list-package-dirs" doesn't tell us dependencies when
     // an error occurs, so just assume there is one dependency, "pubspec.lock".
-    List<String> dependencies = <String>[
-      resourceProvider.pathContext.join(folder.path, PUBSPEC_LOCK_NAME)
-    ];
+    String lockPath = getPubspecLockPath(folder);
+    List<String> dependencies = <String>[lockPath];
     return new PackageMapInfo(null, dependencies.toSet());
   }
 
   /**
+   * Return the path to the `pubspec.lock` file in the given [folder].
+   */
+  String getPubspecLockPath(Folder folder) =>
+      resourceProvider.pathContext.join(folder.path, PUBSPEC_LOCK_NAME);
+
+  /**
    * Decode the JSON output from pub into a package map.  Paths in the
    * output are considered relative to [folder].
    */
   PackageMapInfo parsePackageMap(Map obj, Folder folder) {
     // The output of pub looks like this:
     // {
     //   "packages": {
     //     "foo": "path/to/foo",
     //     "bar": ["path/to/bar1", "path/to/bar2"],
     //     "myapp": "path/to/myapp",  // self link is included
@@ skipping 46 matching lines @@
     String workingDirectory = folder.path;
     int subprocessId = AnalysisEngine.instance.instrumentationService
         .logSubprocessStart(executablePath, arguments, workingDirectory);
     io.ProcessResult result = io.Process
         .runSync(executablePath, arguments, workingDirectory: workingDirectory);
     AnalysisEngine.instance.instrumentationService.logSubprocessResult(
         subprocessId, result.exitCode, result.stdout, result.stderr);
     return result;
   }
 }